^34 



PHANEROGAMS. 



The Embryo generally attains but very small dimensions in the small- seeded 

 parasites and saprophytes destitute of chlorophyll, and remains without differentiation 

 until the time of ripening of the seed ; in Monotropa it never consists of more than 

 two cells, and even in Pyrola secunda, which possesses chlorophyll, only of from eight 

 to sixteen (Hofmeister). The ripe seeds of Orobanche, Balanophora, Rafflesiaceae, 

 &c. contain a very small undifferentiated embryo in the form of a roundish mass of 

 tissue ; the embryo of Cuscuta is of moderate size and length, but the formation of 

 leaves and roots on the filiform stem ^ is suppressed. The Mistletoe (Loranthaceae), 

 on the other hand, parasitic but containing chlorophyll, produces an embryo which 

 is not only large but well-developed. 



If the embryo of the ripe seed is differentiated, as is generally the case, it 

 consists of an axis and two opposite primary leaves (cotyledons) between which the 

 axis terminates as a naked vegetative cone {Cucurbiia)^ or bears a bud which some- 

 times consists of several leaves {Vicia Faba^ Fig. 436, Phaseolus, Quercus^ &c.). 

 Instead of the two opposite cotyledons, a whorl of three is not unfrequently formed 

 in those plants which normally possess only two ^ {Phaseolus, Amygdalus^ Quercus, 

 &c.). The opposite cotyledons are usually alike in form and vigour; in Trapa 

 however one remains much smaller than the other ; and cases even occur in which 



Fig. i^'i.^.—Chunonanthnsfragrans: A horizontal section of the nearly ripe fruit ; B lottgituditial section of the 

 same, /"the thin pericarp, e remains of the endosperm, c cotyledons ; C the embryo removed from the seed, showing 

 the cotyledons rolled round one another, the radicular end below. 



only one has been formed, as in Ranunculus Fi'cana^, where it remains below in 

 the form of a sheath, and in Bulbocapnos, a section of Corydalis^. The two coty- 

 ledons generally form by far the larger part of the ripe embryo, so that the axis 

 has the appearance only of a small fusiform appendage between them ; and this 

 structure is especially striking when the embryo attains a very considerable absolute 

 size in those seeds which possess no endosperm, and the cotyledons swell up into 

 two thick fleshy bodies (as in jEscuIus^ Castanea, Quercus, Fig. 438, Amygdalus, 

 Vicia Faba, Phaseolus, the Brazil-nut, &c.) ; but more often the cotyledons remain 

 thin like shortly stalked foliage-leaves of simple form (as in Cruciferae, Euphor- 

 biaceae, and Tili'a, the last with a three- to five-lobed lamina). Most often they 



* According to Uloth (Flora, i860, p. 265) the root- cap is also absent. On parasites see 

 especially Solms-Laubach in Jahrb. fiir wissensch, Bot. vol. VI. pp. 599 et seq. [Uloth's statement is 

 confirmed by Koch (Ueb, die Entwick. der Cuscuteen, Hanstein's Bot. Abhdl. II. 1874).] 



* Numerous additional instances are given in the Bot. Zeitg. 1869, p. 875. [Masters, Vegetable 

 Teratology, Ray Soc. 1869, p. 370.] 



^ Irmisch, Beitrage zur vergleichenden Morphologic der Pflanzen, Halle 1854, p. 12. 



* [To these instances of what is termed a ' pseudo-monocotyledonous' development may be 

 added Carum Bulbocastanum (see Hegelmaier, Entwick. dicot. Keime, 1878).] 



